code: def expected_length(self, audio):
      n_t = audio.shape[-1]
      frame_size = ddsp.spectral_ops.CREPE_FRAME_SIZE
      hop_size = int(self.sample_rate // self.frame_rate)
      expected_len, _ = ddsp.spectral_ops.get_framed_lengths(
          n_t, frame_size, hop_size
      )
      return expected_len
  
imports: from unittest import mock
  from absl.testing import parameterized
  import ddsp
  from ddsp.test_util import gen_np_batched_sinusoids
  from ddsp.test_util import gen_np_sinusoid
  import ddsp.training.metrics
  import numpy
  import tensorflow.compat.v2
label_desc: Use image node_id 2 for calling the ComputeAudioFeaturesTest obj's underlying member method code with example usage: obj.expected_length(audio) and returns: expected_len